The present invention generally relates to image reading apparatuses, and more particularly to an image reading apparatus using a plurality of photoelectric conversion elements or image sensors.
A digital copying machine, a facsimile machine, an information filing system and an input device for computer aided design (CAD) are examples of the kind of image reading apparatus which uses a plurality of image sensors and reads an image by projecting the image on the image sensors.
Conventionally, in this kind of image reading apparatus, one line data is put together from outputs of the image sensors as follows. That is, there is an overlap of image information between the projections on two mutually adjacent image sensors. Hence, when connecting the output signals of the two mutually adjacent image sensors so as to obtain one line data, a connecting position of the output signal of a first of the two mutually adjacent image sensors is fixed while a connecting position of the output signal of a second of the two mutually adjacent image sensors is variably adjusted depending on the overlap quantity. This adjustment is made by an adjusting means such as a dip switch.
However, when imaging the image of a document surface onto the image sensors by use of lenses, the resolution deteriorates and the quantity of incident light to the image sensors decreases at the edge portion of the lens. For this reason, when the connecting position of the output signal of the first of the two mutually adjacent image sensors is fixed, the connecting position of the output signal of the second of the two mutually adjacent image sensors may be located at a position where the resolution is poor or the quantity of incident light is reduced depending on the overlap quantity.
In addition, when the resolution and the quantity of incident light are unbalanced between the two mutually adjacent image sensors, the read image may look unnatural at the connecting position in the one line data where the output signals of the two mutually adjacent image sensors connect.
On the other hand, in the conventional image reading apparatus using the image sensors, the read-out sequence of the picture element data is changed by taking into account the overlap quantity between the two mutually adjacent image sensors in order to obtain the output image information from the image sensors. No consideration is given as to the effective number of picture elements. In addition, the image information corresponding to the right and left ends of the image becomes indefinite, and a white line or a black line may appear at the right and left ends of a printed image when the read image information is supplied to a printer.